Stimulation of phospholipid N-methylation by isoproterenol in rat hearts.
Phosphatidylethanolamine (PtdEtn) N-methyltransferase activities were studied in rat heart sarcolemmal and sarcoplasmic reticular fractions after a single intraperitoneal injection of isoproterenol (0.5-5.0 mg/kg). Three active sites (I, II, and III) for PtdEtn N-methylation were assayed by measurement of [3H]methyl group incorporation from 0.055, 10, and 150 microM S-adenosyl-L-[methyl-3H]methionine into membrane PtdEtn molecules. Total methylation activity for catalytic site I of both sarcolemma and sarcoplasmic reticulum was stimulated within 2 minutes by isoproterenol in a dose-dependent manner. Although the increased methyltransferase activity in sarcoplasmic reticulum was normalized at 10 minutes, the enzyme activity in sarcolemma was normalized at 5 minutes but was again increased at 10-30 minutes after isoproterenol injection. No changes in response to isoproterenol were seen for site II and III N-methylation activities in either membrane. Individual N-methylated phospholipids (phosphatidyl-N-monomethylethanolamine, phosphatidyl-N,N-dimethylethanolamine, and phosphatidylcholine), which specifically formed at each site, showed similar behavior. Pretreatment of the animals with a beta-blocking drug, atenolol, for 2 days prevented the isoproterenol-induced changes in hemodynamic parameters and sarcolemmal methylation without affecting the enhanced methylation activities in sarcoplasmic reticulum. In vitro addition of cyclic AMP-dependent protein kinase (catalytic subunit) plus Mg-ATP enhanced methyltransferase activities in sarcolemma and sarcoplasmic reticulum from control hearts by 2.7- and 2.3-fold, respectively; however, under the same in vitro conditions, only about 20% activation was seen in both subcellular membranes isolated from the heart of isoproterenol-injected animals.(ABSTRACT TRUNCATED AT 250 WORDS)
Taira
Y
Y
Division of Cardiovascular Sciences, St. Boniface General Hospital Research Centre, Winnipeg, Manitoba, Canada.
Panagia
V
V
Shah
K R
KR
Beamish
R E
RE
Dhalla
N S
NS
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001262:Atenolol / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D007274:Injections, Intraperitoneal; D007545:Isoproterenol / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D008745:Methylation; D008780:Methyltransferases / Q000378:metabolism*; D009206:Myocardium / Q000201:enzymology / Q000378:metabolism*; D050918:Phosphatidylethanolamine N-Methyltransferase; D011494:Protein Kinases / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012508:Sarcolemma / Q000201:enzymology; D012519:Sarcoplasmic Reticulum / Q000201:enzymology; D013268:Stimulation, Chemical
D001262:Atenolol; D000255:Adenosine Triphosphate; D008780:Methyltransferases; C494489:PEMT protein, human; D050918:Phosphatidylethanolamine N-Methyltransferase; D011494:Protein Kinases; D007545:Isoproterenol